Inductive coupled plasma (hereinafter called “ICP”) capable of generating low-pressure, high-density plasma, and helicon wave plasma (hereinafter called “helicon”) that generates plasma by causing excitation and propagation of helicon waves have heretofore been known as a plasma source of a plasma treatment apparatus for substrate treatment. Typically, the ICP generates plasma, utilizing an antenna to which radio-frequency power is applied. Typically, the helicon includes the same antenna as the ICP and is further configured in combination with a magnetic circuit so that helicon waves can propagate through plasma.
An example of a configuration of a conventional plasma treatment apparatus will be described with reference to FIG. 15 (Refer to PTL 1). The plasma treatment apparatus is configured with an ICP apparatus. The apparatus includes a substrate treatment chamber 101 that can be held under a reduced pressure therein, a substrate supporting mechanism 102 that supports a substrate 103 in the substrate treatment chamber 101, a gas introduction mechanism 104 that introduces a gas into the substrate treatment chamber 101, an annular antenna 105 for generating plasma in the substrate treatment chamber 101, a radio-frequency power supply 106 that supplies radio-frequency power to the antenna 105, and a matching circuit 107 for providing matching when the radio-frequency power supply 106 supplies the radio-frequency power to the antenna 105. The substrate treatment chamber 101 is formed of a non-metallic portion 101a such as quartz, and a metallic portion 101b made of aluminum or stainless steel or the like. Solenoid coils 108, 109 for diffusing a magnetic field are arranged around the antenna 105. Further, permanent magnets 110 are arranged around the substrate treatment chamber 101, as needed. The permanent magnets 110 are provided in order to suppress plasma losses on wall surfaces of the substrate treatment chamber 101. With the above configuration, direct-current power supplies 111, 112 supply direct-current power to the solenoid coils 108, 109, respectively, thereby to produce a magnetic field in the substrate treatment chamber 101, so that plasma generated in the non-metallic portion 101a of the substrate treatment chamber 101 can be diffused in the metallic portion 101b of the substrate treatment chamber. Incidentally, illustrations of an evacuation mechanism for holding the inside of the substrate treatment chamber 101 under the reduced pressure, a substrate transfer mechanism that transports the substrate 103, a substrate temperature control mechanism, a wall surface temperature control mechanism for the substrate treatment chamber 101, and a gas supply mechanism that feeds the gas to the gas introduction mechanism 104, and others are omitted from FIG. 15 for convenience of explanation.
Next, description will be given with regard to a procedure for substrate treatment using the above-described plasma treatment apparatus. The substrate 103 is transported into the substrate treatment chamber 101 by the substrate transfer mechanism (not shown), and the substrate 103 is fixed on the substrate supporting mechanism 102. A pressure in the substrate treatment chamber 101 is reduced to a predetermined pressure by the evacuation mechanism (not shown), and further, the gas fed from the gas supply mechanism (not shown) is introduced through the gas introduction mechanism 104 into the substrate treatment chamber 101, which is then held under the predetermined pressure. The radio-frequency power supply 106 applies a radio frequency to the antenna 105 through the matching circuit 107 thereby to generate plasma in the substrate treatment chamber 101, and the plasma is used to treat the substrate 103. Incidentally, for excitation of helicon waves, during the application of the radio frequency, the direct-current power supplies 111, 112 feed a direct current to the solenoid coils 108, 109 thereby to form a magnetic field in the substrate treatment chamber 101. At this time, typically, currents in opposite directions pass through the solenoid coils 108, 109.
Meanwhile, PTL 2 discloses an etching apparatus utilizing ECR (electron cyclotron resonance). FIG. 16 shows the ECR (electron cyclotron resonance) etching apparatus disclosed in PTL 2. An apparatus 310 is configured to supply microwaves 314 of 2.45 GHz through a quartz window 313 to an ionization chamber 311a provided in an upper portion of an apparatus body 311, and to induce electric discharge using external magnetic coils 312. Electrons reach a state of cyclotron resonance under the influence of a magnetic field produced by the microwaves 314 and the external magnetic coils 312. The excited electrons cause dissociation of an etching gas 315, thereby generating high-density plasma. Ions produced by electrolytic dissociation enter through a lead electrode 316 along the diverging magnetic field into a process chamber 311b provided in a lower portion of the apparatus body 311, thus enabling good directional (anisotropic) etching. Meanwhile, a supporting substrate 301 is mounted to a substrate holder 318 held at an oblique angle by a tilting stage 317 having any settable angle of tilt, and further, the supporting substrate 301 rotates on a rotating shaft 319 by a motor (not shown). The ECR (electron cyclotron resonance) etching apparatus shown in FIG. 16 forms a thin film of reverse tapered shape by further rotating the rotating shaft 319 with the supporting substrate 301 inclined 90°-α with respect to an ion beam 316a during etching.